This application is based on Japanese Patent Applications No. 2000-52621 filed Feb. 28, 2000 and Nos. 2000-55464, 2000-55470, 2000-55478, 2000-55481 and 2000-56555 filed Mar. 1, 2000, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention generally relates to a vibration damper installed in a vibrative member of a vehicle, for reducing vibration of the vibrative member. More particularly, the present invention is concerned with such a vibration damper which is novel in construction and which is suitably applicable to the vibrative members such as suspension arms, sub flames, body panels, mounting brackets, and vibrative members used in an engine unit and an exhaustion system, for exhibiting an excellent vibration-damping effect with respect to vibrations of these vibrative members.
2. Description of the Related Art
As vibration-damping means for damping or reducing vibration excited in vehicles such as an automotive vehicle, there are known (a) a mass damper wherein a mass member is fixed to a vibrative member, (b) a dynamic damper wherein a mass member is supported by and connected to the vibrative member via a spring member and (c) a damping material which is a sheet-like elastic member and secured to the vibrative member. However, these conventional devices suffer from various potential problems. For example, (a) the mass damper and (b) the dynamic damper both require a relatively large mass of the mass member, and exhibit desired vibration-damping effect only to significantly narrow frequency ranges. (c) The damping material suffers from difficulty in stably exhibiting a desired damping effect, since the damping effect of the damping material is likely to vary depending upon the ambient temperature.
The present assignee has been disclosed in International Publication WO 00/14429 a novel vibration damper used for an automotive vehicle, which includes a housing member having an inner space and fixed to the vibrative member, and an independent mass member which is accommodated in an inner space of the housing member without being bonded to the housing member, so that the independent mass member is displaceable or movable relative to the housing member, while being independent of the housing member. In the disclosed vibration damper, the independent mass member is moved into and impact the housing member, upon application of a vibrational load to the damper, whereby the vibration of the vibrative body is effectively reduced or absorbed based on loss or dissipation of energy caused by sliding friction generated between the abutting surfaces of the mass member and the housing member and caused by collision or impact of the independent mass member against the housing member. This proposed vibration damper is capable of exhibiting a high damping effect over a sufficiently wide frequency range of frequency of input vibrations, while having a relatively small mass of the mass member.
In order to stably establish a desired damping effect of the vibration damper disclosed in the above-indicated document, it is required to precisely control parameters including a distance of spacing or gap between the abutting surface of the independent mass member and the abutting surface of the housing member, and coefficient of restitution of these abutting surfaces, since the damping effects of the disclosed vibration damper depend upon these parameters. The independent mass member is further required to make a bouncing, sliding or rolling motions. Namely, the independent mass member is required to repeatedly impact and bounce off the housing member so as to repeatedly apply impact energy to the housing member, upon application of the vibrational load to the independent mass member.
As a result of intensive studies in an attempted to further developing the vibration damper as described above, the inventors of the present invention have found that a vibration damper having a housing member and a plurality of independent mass members accommodated in the housing member and comprehensively tuned, exhibits a damping effect which is different from that exhibited by the vibration damper wherein the suitably tuned single mass member is accommodated in the housing member. In particular, a difference in the vibration-damping effects have still found between the vibration damper having the plurality of independent mass member and the vibration damper having a single mass member, even if the total mass of the plurality of mass members is made equal to the mass of the single mass member. This difference may stem from that bouncing or restituting characteristics of each of the plurality of mass members are different from those of the single mass member.
It is therefore a first object of this invention to provide an improved vibration-damping device for vehicles, which is capable of exhibiting a desired damping effect with high efficiency.
It is a second object of this invention to provide a method of producing the vibration-damping device of this invention.
The above first object may be attained according to the following modes (1)-(34) and (37)-(44) of the invention, and the second object may be attained according to the following modes (35) and (36) of the invention. Each of these modes of the invention is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the present invention is not limited to those modes of the invention and combinations of the technical features, but may otherwise be recognized based on the thought of the present invention that disclosed in the whole specification and drawings or that may be recognized by those skilled in the art in the light of the disclosure in the whole specification and drawings.
(1) A vibration-damping device for damping vibrations of a vibrative member of a vehicle, comprising: (a) at least one rigid housing member fixedly disposed in the vibrative member; and (b) a plurality of independent mass members disposed non-adhesively and independently in the at least one housing member such that each of the plurality of independent mass members is opposed to the housing member with a given spacing therebetween in a vibration input direction, and is displaceable relative to the housing member, the each of said plurality of independent mass members being independently displaced relative to said housing member so that the independent mass member and the housing member are brought into elastic impact against each other at respective abutting surfaces thereof which are opposed to each other in the vibration input direction.
In the vibration-damping device constructed according to the above mode (1) of the present invention, the plurality of independent mass members are comprehensively tuned. Namely, a ground total of the masses of the plurality of independent mass member is suitably tuned or determined for assuring desired damping characteristics of the present vibration-damping device. Consequently, the required mass of each of the plurality of independent mass members is made relatively smaller, facilitating the relative movement between the each independent mass member and the housing member, upon application of a vibrational load to the damping device. Namely, bouncing movement of the each independent mass member is effectively induced. In this condition, the independent mass members are effectively forced to move into and impact the housing member, whereby the vibration-damping device can exhibit a desired vibration-damping effect with high efficiency. It should be noted that the housing member may be provided as a box-like member or the like, which is made of a rigid material such as metal and which is formed independently of and fixedly attached to a vibrative member as a subject member whose vibrations to be damped. It may be possible to provide the housing member by utilizing an interior space of a hollow portion of the vibrative member, or alternatively by utilizing partially the vibrative member as a part of the housing member.
(2) A vibration-damping device according to the above-indicated mode (1), wherein a total mass of the plurality of independent mass members is held within a range of 5-10% of a mass of the vibrative member.
Namely, if the total mass of the plurality of independent mass members is smaller than 5% of the mass of the vibrative member, the vibration-damping device possibly suffers from difficulty in exhibiting a desired damping effect, and if the total mass of the plurality of independent mass members is larger than 10% of the mass of the vibrative member, the vibration-damping device suffers from a problem of increase in the overall weight of the device.
(3) A vibration-damping device according to the above-indicated mode (1) or (2), wherein the each of the plurality of independent mass members has a mass within a range of 10-1000 g.
Namely, if the mass of the each independent mass member is smaller than 10 g, the vibration-damping device may suffer from deterioration of its damping effect owing to impact of the independent mass members against the housing member. If the mass of the independent mass member is larger than 1000 g, the independent mass is less likely to make the bouncing movement or displacement thereof, upon application of the vibrational load to the vibration-damping device. Preferably, the each independent mass member has a mass of 10-300 g, more preferably 10-100 g, yet more preferably 10-50 g. This arrangement permits favorable bouncing movement or displacement of the each independent mass member relative to the housing member.
(4) A vibration-damping device according to any one of the above-indicated modes (1)-(3), wherein the plurality of independent mass members comprises at least two of the independent mass members, the at least two of the independent mass members being identical with each other.
In this mode (4), the at least two independent mass members have the same characteristics as for the displacements thereof relative to the housing member. This arrangement permits a high capacity of tuning of the vibration-damping device with respect to a specific frequency vibration, resulting in a significantly improved damping effect of the vibration-damping device with respect to vibrations in a predetermined frequency band.
(5) A vibration-damping device according to any one of the above-indicated modes (1)-(4), wherein at least one of the plurality of independent mass members is tuned differently from the other independent mass members.
In this mode (5), the vibration-damping device can exhibit an excellent vibration-damping effect with respect to the input vibrations having different frequency bands, or over a relatively wider frequency range. Different tuning of the independent mass members may be effected by varying properties of the independent mass members, in terms of a mass and a coefficient of restitution with respect to the housing member, or by varying the spacing between the abutting surfaces of the independent mass members and the housing member.
(6) A vibration-damping device according to any one of the above-indicated modes (1)-(5), wherein at least one of the plurality of independent mass members includes a mass body made of a rigid material.
Namely, each of the plurality of independent mass members may be entirely formed of a rubber elastic body, a synthetic resin material, or a foamed body of the rubber or synthetic resin materials. In order to reinforce the independent mass member, it may be possible to bond a rigid members made of metal to the independent mass member formed of the above-indicated elastic body or the foamed body. According to the above mode (6), the independent mass member includes the mass body formed of rigid materials having higher gravity such as metal or stones, whereby the independent mass member is made compact in size and has a sufficiently large mass thereof. This arrangement results in a decrease in overall size of the vibration-damping device. In the case where the independent mass member includes the mass body formed of the rigid materials, at least one of the abutting surfaces of the independent mass member and the housing member may be formed of an elastic layer made of a rubber elastic body or a synthetic resin material.
(7) A vibration-damping device according to any one of the above-indicated modes (1)-(6), wherein the at least one housing member includes a space for accommodating at least one of the plurality of independent mass members, which space is separated from the external space.
This arrangement is effective to prevent entrance of contaminants or water between the abutting surfaces of the independent mass member and the housing member, whereby the vibration damping effect according to this mode (7) can exhibit a desired damping effect with high stability, leading to improved reliability and durability of the device.
The construction of the housing member is not particularly limited. The portion or region of the housing member used as the space for accommodating the at least one of the plurality of independent mass members (hereinafter referred to as the xe2x80x9cmass member accommodating spacexe2x80x9d) is not particularly limited, but may be determined while taking into account the configuration and construction of the housing, vibration mode of the input vibrations, as well as the configuration and construction of the independent mass members as employed. In the case of the plate-shaped housing member, for example, a plurality of bores or through holes serving as the mass member accommodation spaces may be formed such that the through holes are independent of each other and are juxtaposed with each other in the width direction of the housing member. In the case of the thick-walled housing member, such a plurality of bore or through holes serving as the mass member accommodation spaces can be formed in series in the wall thickness direction of the housing member. In the case of the longitudinal housing member, the plurality of bores each serving as the mass member accommodation space may be arranged in series in the longitudinal direction of the housing member, or alternatively at least one through hole extending through the housing member in the longitudinal direction is formed as the mass member accommodation space and receives a plurality of the independent mass members.
(8) A vibration-damping device according to any one of the above-indicated modes (1)-(7), wherein the at least one housing member is formed with a plurality of through holes which are independent of each other and extend parallel to each other, each of the through holes being adapted to accommodate at least one of the plurality of independent mass members.
In this mode (8), the housing member facilitates arrangement of the plurality of independent mass member. This housing member can be effectively formed by extrusion of an aluminum alloy. Namely, an extruded product of the aluminum alloy has the plurality of through holes continuously extending in the protruding direction. The extruded product is cut off by a suitable length, thereby providing the housing member.
(9) A vibration-damping device according to any one of the above-indicated modes (1)-(8), wherein the at least one housing member has a supporting rod, and at least one of the plurality of independent mass members has an annular block shape and is disposed radially outwardly of the supporting rod of the housing member, the at least one independent mass member being brought into elastic impact against an outer circumferential surface of the supporting rod, upon application of a vibrational load.
This arrangement eliminates a need for the rigid housing member disposed outwardly of the independent mass member, leading to reduction in the overall size of the vibration-damping device, while maintaining a sufficient mass of the independent mass member. In addition, the abutting surfaces of the housing member (i.e., the supporting rod) and the abutting surface of independent mass member (i.e., the annular block) can be made cylindrical, whereby the vibration damping device can exhibit high damping effect with respect to vibrations applied in any radial directions perpendicular to an axis of the supporting rod.
(10) A vibration-damping device according to any one of the above modes (1)-(9), wherein a plurality of the independent mass members are connected with each other via a flexible connecting member such that the plurality of the independent mass members are separately displaceable relative to each other, and the at least one housing member having a plurality of accommodation spaces which are substantially continuous with each other and cooperate to accommodate the plurality of the independent mass members.
According to the present invention, the plurality of independent mass members are only required to be physically independent of the housing member, and to be substantially displaceable or movable separate from each other, when the vibrational loads are applied to the vibration-damping device. The arrangement according to the above mode (10) allows easier handing of the plurality of independent mass members. The plurality of independent mass members flexibly connected with each other may be installed in accommodation spaces formed in the housing member, which are substantially continuous with each other and cooperate to accommodate the plurality of said independent mass members. This arrangement facilitates manufacture of the desired vibration-damping device. The appropriately selection of a material for the connecting member is effective to stabilize a state of the displacement of each of the plurality of independent mass members and a resultant state of impact of the each independent mass member against the housing member.
(11) A vibration-damping device according to any one of the above-indicated mode (1)-(10), wherein at least one of the abutting surfaces of the housing and the independent mass members has a Shore D hardness of 80 or lower, as measured in accordance with ASTM method D-2240.
Namely, hardness or other properties of the abutting surfaces of the independent mass member and the housing member may preferably be held within a given range, in order to assure an improved damping effect of the present vibration-damping device and a reduced impact noise upon impact of the abutting surfaces of the independent mass member and the housing member. In this mode (11), the abutting surfaces are arranged to have a Shore D hardness of 80 or lower, more preferably, within a range of 20-40. For the same technical attempt, the abutting surfaces of the independent mass member and the housing member may preferably be arranged to have a modulus of elasticity within a range of 1-104 MPa, more preferably, 1-103 MPa, and a loss tangent is not less than 1031 3, more preferably within a range of 0.01-10, preferably.
(12) A vibration-damping device according to any one of the above-indicated modes (1)-(11), wherein the at least one housing member is formed of a rigid material having a modulus of elasticity of 5xc3x97103 MPa or more.
It is noted that a high damping effect of the device and a reduced impact noise upon impact of the independent mass member against the housing member may be achieved by suitably controlling coefficient of restitution between the independent mass member and the housing member. In this respect, the housing member may be formed of a rigid material having a modulus of elasticity of 5xc3x97103 MPa or more. For instance, the housing member is desirably formed of a metallic material such as iron. Alternatively, the housing member is formed of rigid materials having a relatively low rigidity, e.g., a rigid resin material having a modulus of elasticity within a range of 5xc3x97103-5xc3x97104 MPa. The use of the housing member formed of the rigid materials having a relatively low rigidity, is effective to minimize the impact noise and to improve damping characteristics of the vibration-damping device with respect to a low frequency band. In the case where the housing member has a relatively low rigidity, the abutting surfaces may be suitably arranged to have a modulus of elasticity which is made smaller than that of the housing member. More preferably, the modulus of elasticity of the abutting surfaces is held within a range of 1-100 MPa. This arrangement permits a desired strength and durability of the housing member, and an improved damping effect of the vibration-damping device with respect to low frequency vibrations, for example.
(13) A vibration-damping device according to any one of the above-indicated modes (1)-(12), wherein the given spacing between the abutting surface of the each of the plurality of independent mass member and the abutting surface of the at least one housing member has a distance within a range of 0.05-0.8 mm, and the each independent mass member may be reciprocally movable by a distance of 0.1-1.6 mm between at least two abutting surfaces of the housing member which are opposed to each other in the vibration input direction, with the independent mass member therebetween.
In this mode (13), the each independent mass member is brought into elastic impact at its both sides, which are opposed to each other in the vibration input direction, against the respective abutting surfaces of the housing member which are opposed to each other with the independent mass member therebetween in the vibration input direction. In particular, the distance of the reciprocal movement of the independent mass member between the abutting surfaces of the housing member is determined within a range of 0.1-1.6 mm, whereby the vibration-damping device can exhibit high damping effect with respect to high frequency vibrations over the wide frequency range, which vibrations are likely to be excited in the vehicles and desired to be damped.
It should be noted that the configuration and the structure of the independent mass member are not particularly limited, but may be suitably determined taking into account characteristics of a location to which the vibration damping device is fixed, and the configuration of the housing member.
(14) A vibration-damping device according to any one of the above-indicated modes (1)-(13), wherein at least one of the plurality of independent mass members has a flat-plate shape, and the at least one housing member includes an accommodation space for accommodating the flat-plate shaped independent mass member, the flat-plate shaped independent mass member having opposite surfaces thereof which are opposed to each other in a thickness direction thereof, and which are opposed to respective portions of an inner surface of the housing member in the vibration input direction, at least one of each of the opposite major surfaces of the flat-plate shaped independent mass member and the corresponding opposite portion of the inner surface of the housing member including a partially protruding portion having a plane protruding end face which serves as the abutting surface.
Namely, intensive analysis of the present inventor has revealed that the flat-plate shaped independent mass member is likely to excite its bouncing movement or displacement relative to the housing member, whereby the vibration-damping device using the flat-plate shaped independent mass members can effectively exhibit an excellent damping effect based on impact of the independent mass members against the at least one housing member. In addition, the presence of the partially protruding portions formed on at least one of the mutually opposite surfaces of the independent mass member and the housing member causes partial impacts of the mutually opposite surfaces of the independent mass member and the housing member. This arrangement facilitates the bouncing movement or displacement of the independent mass member, resulting in further improved damping effect of the vibration-damping device. While the technical reasons for this improvement of the damping effect have not yet been revealed, it may be considered as follow: The each flat-plate shaped mass member installed in position with its opposite major surfaces opposed to each other in the vibration input direction, has a higher weight distribution in the vibration input direction, in comparison with that of the spherical mass, leading to difficulty in assuring the bouncing movement of the independent mass member with a horizontal attitude with respect to the vibration input direction. Namely, the independent mass member is likely to make a slight displacement about its center axis in the width direction thereof and a rolling displacement about its center axis in the longitudinal direction. Thus, the flat-plate shaped independent mass member is likely to be displaceable or movable upon application of the vibrational load.
The partially protruding portion may be formed on any one of the mutually opposite surfaces of the independent mass member and the housing member. The height, number, configuration, size or other features of the partially protruding portion are not particularly limited, but may be determined, taking into account the configuration, size and mass of the independent mass member, so that the independent mass member and the housing member are brought into impact against each other only at the partially protruding portion formed thereon. A material for forming the partially protruding portion is not particularly limited. For instance, the partially protruding portion may be made of elastic materials such as a rubber elastic body and a synthetic resin material, or alternatively may be made of rigid materials such as metal. In the case where the partially protruding portion is made of a rigid material, at least one of the protruding end face of the partially protruding portion and the corresponding abutting surface on which the partially protruding portion is brought into impact, may be covered with an elastic layer, e.g., a rubber elastic body layer.
(15) A vibration-damping device according to the above-indicated mode (14), wherein the flat-plate shaped independent mass member includes a flat-plate shaped mass body made of metal and having opposite plane surfaces which are opposed to each other in a thickness direction thereof, and which are opposed to respective portions of the inner surface of the housing member in the vibration input direction, and an elastic layer formed on and secured to a surface of the flag-plate shaped mass body, the partially protruding portion being formed of the elastic layer.
In this mode (15), the use of the metallic flat-plate shaped mass body permits a sufficiently high gravity of the independent mass member with ease. Further, the presence of the partially protruding portion formed of the elastic layer can assure the partial impact of the independent mass member against the housing member. The elastic layer may be made of a rubber material. For instance, the elastic layer may be formed on and secured to the mass body, upon vulcanization of a rubber material for forming the elastic layer within a mold for forming the elastic layer, for example. Alternatively, the elastic layer may be fixedly formed by coating a liquid rubber on the surface of the mass body. Further, the elastic layer may also be formed as an attachment in the form of a cap, a ring, or the like, which is removably inserted onto the outer surface of the mass body. Since the partially protruding portion is formed on the side of the independent mass member, the independent mass member and the housing member may be impacted against each other with a stabilized abutting surface area, in comparison with the partially protruding portion which is formed on the side of the housing member.
(16) A vibration-damping device according to the above-indicated mode (14) or (15), wherein the flat-plate shaped independent mass member having a rectangular shape, and including the partially protruding portions formed at longitudinally opposite end portions thereof, respectively.
In this mode (16), the rectangular shaped independent mass member is brought into impact against the housing member at its longitudinally opposite end portions. This arrangement is effective to induce the bouncing displacement of the independent mass member relative to the housing member upon application of the vibrational load to the device. It may be possible that the partially protruding portions are formed on the corresponding portions of the inner surface of the housing member, instead of on the longitudinally opposite sides of the independent mass member.
In the above-indicated modes (15) and (16), the partially protruding portion may be formed on one or both of the opposite surfaces of the independent mass member. In the case where the partially protruding portion is formed on one of the opposite surfaces of the independent mass member, the partially protruding portion preferably be formed on the vertically lower one of the opposite surfaces, which is held in contact with the housing member due to the gravity acting thereon in the static state of the device.
(17) A vibration-damping device according to any one of the above-indicated modes (14)-(16), wherein the opposite surfaces of the flat-plate shaped independent mass member include partially protruding portions, respectively.
In this mode (17), the independent mass member impact via their partially protruding portions against the housing member, in both opposite surfaces thereof which are opposed to each other in the vibration input direction. This arrangement further induces the bouncing displacement of the independent mass member relative to he housing member, whereby the vibration damping device can exhibit further improved damping effect based on the impact of the independent mass member against the housing member.
(18) A vibration-damping device according to any one of the above-indicated modes (1)-(17), wherein at least one of the plurality of independent mass member includes at least one abutting projection in the form of a projection or a ridge, which is formed at a surface thereof which are opposed to the housing member in the vibration input direction, the at least one abutting projection being made of an elastic material, protruding toward the housing member in the vibration input direction, and having a protruding end portion serving as the abutting surface of the independent mass member.
In this mode (18), the abutting surface of the independent mass member can be provided by the abutting projection that is made of an elastic material and has a relatively large free surface for deformation. This arrangement permits low dynamic spring characteristics of the abutting surface of the independent mass member, whereby resonance frequency of the bouncing movement of the independent mass member can be tuned to a low frequency band. Owing to the resonance of the independent mass member, the independent mass member can provide its bouncing displacement and repeatedly impacted against the housing member upon application of the low frequency vibrations, even if the applied vibration energy is relatively small. Thus, the vibration-damping device according to the present mode (18) of the invention can exhibit high damping effect even for the low frequency vibration.
Preferably, the abutting projection may be formed of an elastic material and has a Shore D hardness of 80 or lower, more preferably within a range of 20-40 as measured in accordance with ASTM method D-2240. The configuration of the abutting projection may be suitably determined, taking into account the configuration of the independent mass member and the desired elasticity of the abutting projection. For instance, the abutting projection may be a straight or curved ridge extending continuously or discontinuously in a desired direction, or alternatively may be a plurality of projections which are independent with each other. The abutting projection is hopefully compressively deformed upon abutting contact with the housing member, leading to high durability of the abutting projection.
The size, number, material and other features of the abutting projection are not particularly limited, but may be suitably determined depending upon the mass of the independent mass member and required vibration damping characteristics of the vibration damping device, while taking into account required vibration damping effects and durability of the elements.
(19) A vibration-damping device according to the above-indicated mode (18), wherein the at least one abutting projection has a height within a range of 0.5-1.0 mm and a width within a range of 1.0-3.0 mm.
(20) A vibration-damping device according to the above-indicated mode (18) or (19), wherein the protruding end portion of the at least one abutting projection has a tapered shape.
(21) A vibration-damping device according to any one of the above-indicated modes (18)-(20), wherein the at least one independent mass member is a longitudinally extended member, and the abutting projection is a ridge formed on the outer circumferential surface of the independent mass member and continuously extending in a circumferential direction of the independent mass member.
In the above-indicated modes (18)-(21), each of the plurality of independent mass members may be entirely formed of a rubber elastic body, a synthetic resin material, or a foamed body of the rubber or synthetic resin materials. In order to reinforce the independent mass member, it may be possible to bond a rigid members made of metal to the independent mass member formed of the above-indicated elastic body or the foamed body. In the case where the independent mass member is formed of the elastic material, the abutting projection is integrally formed with the independent mass member, preferably. This arrangement permits a simple construction and improved manufacturing efficiency of the independent mass member. Alternatively, the independent mass member includes a mass body formed of a rigid material having a higher gravity such as metal or stones.
(22) A vibration-damping device according to any one of the above-indicated modes (18)-(21), wherein the at least one independent mass member includes a rigid mass body, the abutting projection formed of an elastic material being formed on an outer circumferential surface of the rigid mass body.
This arrangement of the mode (22) makes it possible to provide the independent mass member which is made compact in size and which is large in mass. The use of the rigid mass body is effective to prevent deformation of the independent mass member overall, leading to stability in characteristics of the displacement of the independent mass member and in the vibration damping effect of the damping device.
(23) A vibration-damping device according to the above-indicated mode (22), wherein the at least one independent mass member further includes an elastic layer formed on and bonded to an entire surface of the circumferential surface of the mass body with a constant thickness, the abutting projection being integrally formed on the outer surface of the elastic layer.
According to this mode (23), the resonance frequency of the bouncing movement of the independent mass member can be tuned to a lower frequency band, resulting in a high degree of freedom in tuning the resonance frequency of the vibration-damping device.
In the above-indicated modes (18)-(23), the abutting projection may be formed independently of the independent mass member. For instance, the abutting projection may be integrally formed on an outer surface of an attachment in the form of a cap or a cover, which is removably inserted onto the outer surface of the mass body.
(24) A vibration-damping device according to any one of the above-indicated modes (18)-(23), wherein the at least one independent mass member includes a rigid mass body longitudinally extending with a constant cross sectional shape, and the abutting projection is formed of an elastic ring inserted onto an outer circumferential surface of the independent mass member.
The use of the elastic ring permits an easy formation of the abutting projection in the form of the ridge. This arrangement also facilitates replacement of the abutting projection. In this respect, the independent mass member may have a positioning groove formed in its outer circumferential surface, for facilitating positioning of the elastic ring relative to the independent member, upon replacement thereof.
Meanwhile, intensive studies have been made by the inventors of the present invention on the vibration damping device according to any of the above-indicated modes (1)-(24) of the present invention, and have revealed that damping effects of the vibration damping device depend upon parameters such as a mass of the independent mass member, a distance of spacing or gap between the abutting surface of the independent mass member and the abutting surface of the housing member, and modulus of elasticity or coefficient of restitution between these abutting surfaces. In order to stably establish a desired damping effect of the vibration-damping device, it is required to precisely control these parameters so as to excite repeated bouncing movement of the independent mass member and resultant repeated impact of the independent mass member against the housing member, thereby applying repeatedly impact energy to the housing member, upon application of the vibrational load to the independent mass member. As a result of the extensive analysis conducted by the inventors, it was also revealed that the vibration damping devices which are made identical with each other in terms of the mass of the independent mass member, the coefficient of restitution between these abutting surfaces, the distance of spacing between the abutting surface, or the like, still exhibit different damping effects due to variations in conditions of impact and bounce of the independent mass member against and from the housing member.
It was further revealed that friction between the abutting surfaces of the independent member and the housing member has great impact on the damping effect of the vibration damping device in which the independent mass member is opposed to the housing member with the slightly small spacing therebetween and is oscillated at a relatively high frequency in a complicated displacement condition. The further studies have been made in view of the above, and result in a vibration-damping device constructed according to the mode (25) of the present invention.
(25) A vibration-damping device according to any one of the above-indicated modes (1)-(24), wherein at least one of the plurality of independent mass member being arranged such that at least one of the abutting surface of the independent mass member and the abutting surface of the housing member is formed of a rubber elastic body, the at least one independent mass member and the at least one housing member being impacted against each other via the rubber elastic body with a coefficient of kinetic friction of 0.4 or lower between the abutting surfaces thereof.
In this mode (25), the independent mass member is likely to be displaced relative to the housing member. Namely, the arrangement of the present mode facilitates the bounding displacement of the independent mass member relative to the housing member, resulting in high damping effect based of the vibration damping device based on the impact of the independent mass member against the housing member. Since the kinetic friction between the abutting surfaces of the independent mass member and the housing member is suitably arranged as indicated above, the independent mass member is less likely to suffer from or free from a trouble of its displacement, e.g., sticking of the mass member to the housing member. Thus, the vibration-damping device of the present invention can exhibit a desired damping effect with high stability. In this respect, the xe2x80x9ccoefficient of kinetic frictionxe2x80x9d is interpreted to mean a coefficient of friction between two surfaces which are sliding over each other. The rubber elastic body may be applicable to both of the abutting surfaces of the independent mass member and the housing member, which surfaces are opposed to each other in the primary vibrational load receiving direction. Further, the rubber elastic body is also applicable to the abutting surfaces of the independent mass member and the housing member which are opposed to each other in the direction perpendicular to the primary vibrational load receiving direction.
(26) A vibration-damping device according to the above-indicated mode (25), wherein the rubber elastic body is subjected to a surface treatment by hydrochloric acid.
This arrangement of the mode (26) makes it possible to change the surface condition of the rubber elastic body for decreasing the coefficient of kinetic friction, while maintaining spring characteristics of the whole rubber elastic body. A rubber material for forming the rubber elastic body may be selected from natural rubber and diene rubbers having a double bond in a primary chain, such as isoprene rubber, butadiene rubber, butyl rubber, styrene-butadiene rubber, nitrile rubber, chloroprene rubber. The selected rubber material is vulcanized, thereby providing the rubber elastic body. A surface hardening treatment is executed on the obtained rubber elastic body by simply dropping the rubber elastic body to a hydrochloric acid aqueous solution having a predetermined concentration of the hydrochloric acid. As a result of the surface hardening treatment, a chlorine layer (i.e., a replacement of the double bond by the chlorine) is formed on the outer surface of the rubber elastic body. The thickness of the chlorine layer is preferably determined within a range of 1-20 xcexcm, so as to prevent a significant deterioration of the spring characteristics of the rubber elastic body, and assure a desired durability of the layer.
(27) A vibration-damping device according to the above-indicated mode (25) or (26), wherein the rubber elastic body being coated by a low-frictional thin resin layer secured thereto.
In this mode (27), the thickness of the low-frictional resin layer formed on the surface of the elastic body layer is made smaller sufficiently, making it possible to maintain the spring characteristics and coefficient of restitution of the whole rubber elastic body, while decreasing the coefficient of the kinetic friction of the surface of the rubber elastic body. It is noted that the surface of the rubber elastic body is required to exhibit desired wear resistance, elasticity and flexibility. To meet these requirements, a material for the thin resin layer is preferably selected from a group consisting of fluororesin, polyamide resin and the like. The thickness of the thin resin layer is generally determined within a range of 10-50 xcexcm, so as to prevent a significant deterioration of the spring characteristics of the rubber elastic body. The method for forming the thin resin layer is not particularly limited. For instance, a resin sheet is laminated on the surface of the rubber elastic body and is fused by heat application, thereby providing the thin resin layer adhered to the outer surface of the rubber elastic body. For forming the thin resin layer with high stability, the thin resin layer may be preferably as follow: First, a powdered resin materials is applied and stuck on the outer surface of the rubber elastic body, by means of electrostatic coating. The powdered resin is fused by heat application, e.g., by heat ray irradiation or by induction heating.
(28) A vibration-damping device according to any one of the above-indicated mode (25)-(27), wherein the rubber elastic body is made of a rubber composition which contains at least one of mica, polytetorafluoroethylene, and graphite.
In this mode (28), the rubber elastic body itself is capable of serving as the abutting surface having a low friction coefficient, leading to high durability of the abutting surface, in comparison with the above mentioned thin layers formed on the rubber elastic body. The rubber composition may be mixed with at least one of mica, polytetorafluoroethylene, or graphite at any rate. The amount of the mixture may be determined taking into account characteristics of the employed rubber composition, required characteristics of the abutting surface.
It is to be understood that a combination of two or more of the above-indicated modes (25)-(28) may be employed to establish the coefficient of kinetic friction of 0.4 or lower between abutting surfaces of the independent mass member and the housing member.
In the vibration damping device constructed according to any one of the above-indicated modes (25)-(28), both of the abutting surfaces of the independent mass member and the housing member are preferably constituted by the rubber elastic body, and are subjected to additional treatment or treatments according to any one or more of the above-indicated modes (26)-(28), thereby establishing the coefficient of kinetic friction of 0.4 or lower between the abutting surfaces of the independent mass member and the housing member. Alternatively, one of the abutting surfaces of the independent mass member and the housing member may be constituted by the rubber elastic body which is subjected to one or more of the treatment or treatments according to any one of the above-indicated modes (26)-(28).
(29) A vibration-damping device according to any one of the above-indicated modes (25)-(28), wherein the abutting surface of the independent mass member is formed of the elastic rubber body, while the abutting surface of the housing member is covered by a solid coating layer made of a resin material having a low friction coefficient.
The arrangement of the mode (29) makes it possible to decrease coefficient of friction of the abutting surface of the housing member with ease, even in the case where the abutting surface of the housing member is not constituted by the rubber elastic body. Preferably, the solid coating layer of the low frictional resin is a solid-lubricating layer, more preferably is a solid-lubricating layer formed of a fluororesin by baking coating.
(30) A vibration-damping device according to any one of the above-indicated modes (25)-(29), wherein the independent mass member and the housing member are opposed to each other at respective surfaces which are opposed to each other in the vibration input direction, at least one of the surfaces of the independent mass member and the housing member having a partially protruding portion protruding toward the opposed surface, a protruding end face of the protruding portion serving as the abutting surface, the abutting surface being formed of the rubber elastic body, and a coefficient of kinetic friction between the abutting surfaces of the independent mass member and the housing member is set to 0.4 or lower.
In this mode (30), the protruding end face of the partially protruding portion serves as the abutting surface. This permits decrease in area of the abutting surface, thereby further facilitating movement or displacement of the independent mass member relative to the housing member, upon application of the vibrational load. Thus, the vibration-damping device exhibits high damping effect based on the impact of the independent mass member against the housing member. Namely, the independent mass member may be forced to move or displace not only in the vibration input direction, but also about a plurality of axes of displacement, owing to the decreased abutting surface. Accordingly, it may be considered that the use of the partially protruding portion may provide the substantially same effect caused by the above-mentioned decrease in the coefficient of kinetic friction between the abutting surfaces of the independent mass member and the housing member.
(31) A vibration-damping device according to any one of the above-indicated modes (1)-(30), wherein at least one of the plurality of independent mass member is arranged such that at least one of the independent mass member and the housing member being covered by a coating rubber layer formed of coating of a liquid rubber on a surface thereof, at least one of the abutting surfaces of the independent mass member and the housing member being formed of the coating rubber layer.
In the above mode (31), the coating rubber layer is formed of the liquid rubber by coating, making it possible to form the sufficiently thin rubber layer with high preciseness on the surface of the independent mass member and/or the surface of the housing member, without using a mold for molding the coating rubber layer. Namely, this arrangement permits high dimensional accuracy of the coating rubber layer, resulting in high dimensional accuracy of the spacing between the abutting surfaces of the independent member and the housing member which surfaces are opposed to each other in the vibration input direction. Thus, the vibration-damping device can exhibits desired damping effects with stability. In addition, the coating rubber layer has a wall thickness which is made sufficiently smaller, making it possible to make the size of the independent mass member as large as possible, within a limited accommodation space. In this respect, the independent mass member is made of a high gravity material such as iron, so that the large-sized independent mass member may exhibit improved damping effects.
(32) A vibration-damping device according to the above-mode (31), wherein the coating rubber layer having a thickness within a range of 0.03-0.5 mm.
If the thickness of the coating rubber layer is made smaller than 0.03 mm, the coating rubber layer is likely to be damaged or peeled off from the independent mass member, upon impact of the independent mass member against the housing member, resulting in low durability of the coating rubber layer. If the thickness of the coating rubber layer is made larger than 0.5 mm, the coating rubber layer is likely to suffer from unacceptable distortion thereof due to shrinkage of the liquid rubber upon vulcanization, resulting in difficulty in establishing high dimensional accuracy of the spacing between the abutting surfaces of the independent mass member and the housing member. Therefore, the coating rubber layer having a thickness within a range of 0.03-0.5 mm permits the high dimensional accuracy thereof and the resultant dimensional accuracy of the spacing between the abutting surfaces of the independent mass member and the housing member, while assuring improved durability thereof. More preferably, the thickness of the coating rubber layer is held within a range of 0.05-0.3 mm.
(33) A vibration-damping device according to the above-indicated mode (31) or (32), wherein the abutting surface of the independent mass member is covered by the coating rubber layer, and having a chamfered corner.
In this mode (33), the corner of the abutting surface of the independent mass member is chamfered, so that the portion of the coating rubber layer which covers the chamfered corner of the independent mass member is less likely to suffer from or free from a problem of stress concentration, upon impact of the independent mass member and the housing member. Thus, the coating rubber layer is free from a problem of undesirable damage caused by the stress concentration, and accordingly enjoys improved durability. The chamfered corner may have various configurations, such as a rounded surface, a C-shaped surface, a narrow-width surface and the like. The chamfering may be conducted by an optional method including cutting and pressing.
(34) A vibration-damping device according to any one of the above-indicated modes (31)-(33), wherein the independent mass member is partially covered by the coating rubber layer, and is exposed to the atmosphere at a portion which does not constitute the abutting surface thereof.
In this mode (34), the portion of the independent mass member, which is exposed to the atmosphere, may be utilized for handing the independent mass member. For instance, the coating operation of the liquid rubber may be executed, while the independent mass member being supported at the exposed portion thereof by a suitable support member, whereby the coating operation is performed with high efficiency. Preferably, the independent mass member includes the exposed portion located in one of longitudinally opposite end portions thereof.
(35) A method of manufacturing a vibration-damping device defined in the above-indicated modes (31)-(34), comprising a step of: forming the coating rubber layer on at least one of the independent mass member and the housing member, by coating a liquid rubber on a surface of the at least one of the independent mass member and the housing member.
According to the above mode (35), the coating rubber layer may be formed of the liquid rubber by coating with ease, without needing for a mold. Therefore, the coating rubber layer can be manufactured with simple facilities and with improved efficiency. Further, the thin coating rubber layer can be formed with high dimensional accuracy, according to the method of this mode.
Various kinds of rubber materials or compositions may be employed for preparing the liquid rubber. For instance, the materials for the liquid rubber may be selected from the group consisting of natural rubber, a synthetic rubber including styrene-butadiene rubber, ethylene-propylene rubber, butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, acrylic rubber, isoprene rubber, and elastomeric resin. In view of physical properties, production efficiency, handling of the respective rubber materials, diene rubbers and chlorine rubbers may be employed, preferably. More preferably, a mixture of the natural rubber and diene or chlorine rubbers may be employed. As well known in the art, the prepared rubber composition may also mixed with known additives such as a vulcanizing agent, vulcanizing aid, antioxidant, plasticizer, softener, reinforcing filler, filler and the like. The thus obtained rubber composition is dissolved in a desired solvent, thereby providing the liquid rubber of the prepared rubber composition. The solvent may be suitably determined depending upon the rubber composition. For instance, the solvent may consist solely of toluene, methyl alcohol, cyclohexane, isobutyl methyl ketone, or the like, or may be a mixture of two or more of the above-indicated materials. The above-mentioned components of the liquid rubber may be mixed with each other at a suitable proportion so that the obtained liquid rubber exhibits a desired viscosity suitable for forming the liquid rubber layer with a constant thickness.
The thus prepared liquid rubber may be applied on the surface of the independent mass member and/or the surface of the housing member, by spraying, brush application, roll coater, or the like, preferably, by dipping. Namely, the independent mass member and/or the housing member is immersed in the liquid rubber retained in a suitable container. The liquid rubber coating applied on the surface of the independent mass member and/or the surface of the housing member is then subjected to a drying treatment and the following heating and warming treatment by using hot air. The liquid rubber coating is subjected to a vulcanizing operation as needed.
Before the application of the liquid rubber, the surfaces of the independent mass member and/or the surface of the housing member is preferably subjected to degreasing, cleaning or washing, chemical conversion coating, adhesive treatment, or the like. The adhesive treatment is not essential to practice of the present mode of the invention. It may be possible to provide raised and recessed portions between the coating rubber layer and the surface of the independent mass member or the housing member, whereby the coating rubber layer is adhere to the surface of the independent mass member of the housing member owing to the mechanical engagement of the raised and recessed portions. Namely, the raised and recessed portions constitute an engaging mechanism.
Further, the above-described steps for forming the coating rubber layer is desirably executed after the forming of independent mass member and the housing member is finished. However, it may be possible to finish the forming of the independent mass member and the housing member after the coating rubber layer is formed.
(36) A method of manufacturing a vibration-damping device according to the above-indicated mode (35), wherein the step of forming the coating rubber layer on at least one of the independent mass member and the housing member, is executed a plurality of times to thereby form a lamination of the coating rubber layer.
According to the method of this mode (36), the thickness of the coating rubber layer is suitably adjusted by changing the repetition times of the step of forming the coating rubber layer. In particular, the thickness of the coating rubber layer formed by a single execution of the forming step can be set to tens of micrometer or lower, whereby the thickness of the coating rubber layer can be controlled with high accuracy. For producing the lamination of the coating rubber layer, the following method is preferably employed, for example. First, the coating rubber layer is formed on the surface of the independent mass member or the housing member, according to the above-described step. The formed coating rubber layer is then subjected to a drying treatment. Next, another coating rubber layer is formed on the dried coating rubber layer. This cycle of steps are executed optional number of times, thereby providing the lamination of the coating rubber layer.
(37) A vibration-damping device according to any one of the above-indicated modes (1)-(37), wherein the vibrative member comprises a rotational member which is rotatable about a center axis thereof, and the housing member being fixedly disposed in the rotational member, the abutting surfaces of the independent mass member and the housing member being opposed to each other in a circumferential direction about the center axis of the rotational member.
In the vibration-damping device according to the above mode (37), the each independent mass member is induced to provide its bouncing movement or displacement relative to the housing member in the vibration input direction, upon application of the vibrational load. In this condition, the independent mass member impacts against and bounces off the housing member repeatedly, whereby the vibration of the rotational member as the vibrative member is effectively attenuated or absorbed based on loss or dissipation of energy caused by sliding friction generated between the abutting surfaces of the mass member and the housing member and caused by collision or impact of the independent mass member against the housing member. That is, the vibration damping device constructed according to the above mode (37) exhibits its damping effect owing to impact of the independent mass member on the housing member, rather than the resonance of the mass member, whereby the vibration damping device can exhibit an excellent damping effect with respect to vibrations over a wide frequency range with the mass member whose mass is made smaller than that of the mass member in the conventional vibration damper. Besides, the damping effect of the vibration-damping device is insensitive to the change of the ambient temperature, whereby the vibration-damping device can exhibit a desired damping effect with high stability.
Since the each independent mass member is non-adhesively disposed in the housing member, and accordingly is independently displaceable relative to the housing member, the vibration damping device of the present mode of the invention can exhibit the desired damping effect based on the impact of the independent against the housing member, with respect to any vibrations applied in a direction perpendicular to the center axis of the rotational member, and applied in a rotational direction of the rotational member. Thus, the vibration-damping device is capable of damping various kinds of input vibrations which are different from each other in terms of frequency and direction.
The housing member may be provided as a box-like member or the like, which is made of a rigid material such as metal and which is formed independently of and fixedly attached to the rotational member as a subject member whose vibrations to be damped. This arrangement permits high dimensional accuracy of the housing member with ease, irrespective of any conditions of the rotational member. It may be possible to provide the housing member by utilizing an interior space of a hollow portion of the rotational member, or alternatively by utilizing partially the rotational member as the housing member. In this arrangement, the housing member is made simple in construction and compact.
(38) A vibration-damping device according to the above-indicated mode (37), wherein the housing member is partially constituted by utilizing the rotational member.
With respect to the above-indicated mode (37), the rotational member includes a rotational disk used as a power transmitting member, such as pulleys and gears, which is rotatable about a center axis thereof and extending in the direction perpendicular to the center axis.
(39) A vibration-damping device according to the above-indicated mode (37), wherein the rotational member comprises a power transmitting rotational disk extending in a direction perpendicular to the center axis, the plurality of independent mass members being disposed in a radially intermediate portion of the rotational disk.
In the above mode (39), the housing member may be integrally formed with the rotational disk. Alternatively, the housing member may be formed independently of and fixed to the housing member. Further, the independent mass members are independent of the rotational disk serving as the power-transmitting member. Therefore, the vibration-damping device of this mode (39) may be integrally installed in the rotational disk, without interrupting a rotational power-transmitting path of the rotational disk. Thus, the present vibration-damping device assures high efficiency of the power transmission, and high durability.
Preferably, the each independent mass member including the spacing between the abutting surfaces of the independent mass member and the housing member, is disposed in an interior space which is formed within the housing member and which is separated from the external space. This arrangement is effective to prevent entrance of contaminants or water between the abutting surfaces of the independent mass member and the housing member, leading to high stability of the damping effect of the vibration-damping device. In this respect, the interior space need not to be completely separated from the external area, but may be communicated with the external area through minute communication holes, for thereby avoiding a pressure change in the interior space due to a change in the ambient temperature.
(40) A vibration-damping device according to any one of the above-indicated modes (37)-(39), wherein the plurality of independent mass member are disposed in the rotational member such that the independent mass members being spaced apart from each other in the circumferential direction about the center axis, the independent mass members being arranged such that a center of gravity of overall of the plurality of independent mass members being located on the center axis of the rotational member, upon rotation of the rotational member about the center axis.
The arrangement of this mode (40) is effective to eliminate or minimize a possibility of occurrence of a bending force caused by centrifugal force of the respective independent mass members, which adversely affects on the rotational member, resulting in no need for a balance member. In order to establish a rotation of the rotational member with the gravity of the whole independent mass members being located on the center axis of the rotational member, for example, the plurality of independent mass members are disposed in the rotational member such that the independent mass members are spaced apart from each other in the circumferential direction about the center axis, with a given spacing therebetween, so that the gravity of the all independent mass members are located on the center axis of the rotational member owing to the centrifugal forces acting on the respective independent mass members upon rotation of the rotational member. It may be possible to arrange the vibration damping device of this mode such that the independent mass members is constituted by a plurality of annular mass members and are disposed in the rotational member such that the independent mass members are spaced apart from each other in the axial direction with a given spacing therebetween. This modification also permits the above-indicated rotation of the rotational member with the center of the gravity of the all-independent mass members being located on the center axis of the rotational member.
(41) A vibration-damping device according to the above-indicated mode (40) wherein each of the plurality of independent mass members includes two circumferentially opposite end portions which are opposed to each other in the circumferential direction about the center axis of the rotational member and which serve as the abutting surfaces of the independent mass member, the each of the independent mass member being brought into elastic impact at the circumferentially opposite end portions thereof against the housing member in said circumferential directions about the axis of the rotational member.
In this mode (41), the independent mass members are independent of each other and are independently displaced or moved relative to the housing member. Thus, the vibration-damping device of this mode can exhibit a high damping effect based on the impacts of the respective independent mass members against the housing member. In particular, the each independent mass member has a relatively small mass, facilitating the bouncing displacement of the each independent mass member relative to the housing member, whereby the vibration-damping device can exhibit an improved damping effect. In addition, the centripetal force acting on the each independent mass member by the housing member can be offset or canceled between the independent mass members, thereby eliminating or reducing the possibility of the occurrence of the bending force acting on the rotational member.
(42) A vibration-damping device according to the above-indicated mode (41) wherein at least one of the plurality of independent mass member is constituted by an arcuate block member which extends parallel to the center axis of the rotational member with an arc cross sectional shape which extends in the circumferential direction of the rotational member with a given circumferential length.
The arrangement of the above mode (42) is effective to practice the vibration-damping device according to the above-indicated mode (41). Further, the use of the independent mass member in the form of the arcuate block makes it possible that the independent mass member impact against the housing member with a relatively large abutting surface area in the circumferential direction and in the radial direction perpendicular to the center axis.
(43) A vibration-damping device according to the above-indicated modes (41) or (42), wherein at least one of the plurality of independent mass member is constituted by a solid rod having a circular cross sectional shape and extending parallel to the center axis of the rotational member.
This arrangement of this mode (43) is effective to practice the above-indicated mode (41). The vibration-damping device constructed according to the present mode is capable of exhibiting substantially identical damping effect with respect to vibrations applied in any radial directions perpendicular to a center axis of the independent mass member.
(44) A vibration-damping device according to any one of the above-indicated modes (37)-(39), wherein at least one of the plurality of independent mass member is constituted by an annular mass member continuously extending in the circumferential direction about the center axis of the rotational member, the abutting surfaces of the annular mass member and the housing member being opposed to each other in the circumferential direction about the center axis of the rotational member and being brought into elastic impact against each other in the circumferential direction.
In this mode (44), the annular independent mass member is less likely to suffer from or free from a problem of centrifugal force acting thereon, since the centrifugal force is likely to be canceled, leading to a stable attitude of the annular independent mass member. In one advantageous arrangement of the above preferred mode (44) of the invention, one of the abutting surfaces of the independent mass member and the housing member may be provided with a plurality of engaging recesses, and the other surface may be provided with a plurality of engaging protrusions which are brought into abutting contact with the engaging recesses in the circumferential direction about the center axis of the circumferential direction.